In both cases (i.e. a printer being disconnected or it running out of paper), PrintNode will successfully deliver the print request to the printer spooler and it will be up to the operating system and the printer driver to handle any issues.

From PrintNode's perspective, the job will be processed correctly and PrintNode will report the "done" state for such a print job.

If on the other hand the PrintNode Client running on the computer is disconnected (or simply turned off) the print jobs will await on the PrintNode server and will be sent to the PrintNode Client once it connects.